With the development of wireless communication technology, particularly the near field communication technology, data exchange can be carried out between electronic equipments within a limited range. The near field communication (NFC) technology is a short-distance high-frequency wireless communication technology developed from the radio frequency identification (RFID) technology. Compared to infrared communication and Bluetooth communication, NFC adopts a unique signal attenuation technology to be able to communicate within a very short distance (such as 10 cm). NFC is high in security due to short communication distance, and therefore, it is very suitable to be applied to identity recognition, secure payment, etc.
The NFC communication equipment has three operation modes, i.e., tag mode, card reader mode and point-to-point mode. The tag mode is also known as card mode which is a passive mode. The typical example of the NFC communication equipment operating under the tag mode is ordinary NFC tag which can store information such as personal information, payment information, Bluetooth address information and WIFI address information for reading and is suitable for being applied to posters, identity recognition, wireless secure payment, Bluetooth pairing, WIFI pairing, etc. The card reader mode is an active mode. The NFC communication equipment (such as NFC mobile phone) operating under the card reader mode can read out the stored information from the NFC tag, or even can write the information into the NFC tag. The point-to-point mode is used for data exchange. Specifically, two NFC communication equipments operating under the point-to-point mode can realize point-to-point data transmission, such as downloading music and exchanging pictures.
FIG. 1 is a schematic diagram, showing the operating process of ordinary NFC card reader and NFC tag. As shown in FIG. 1, the ordinary NFC tag comprises an NFC tag chip and an NFC antenna coil. When the NFC card reader is close to the NFC tag, the NFC card reader emits electromagnetic energy to the NFC tag, the NFC antenna coil of the NFC tag is coupled with the electromagnetic energy and transfers the electromagnetic energy to the NFC tag chip which is connected with the NFC antenna coil, and the NFC tag chip converts the electromagnetic energy into power source required by inside circuits such as microcontroller, modem and memory through a rectifying circuit. When circuits such as microcontroller, modem and memory start to work after power on, the information stored in the NFC tag chip can be transmitted to the NFC card reader through the NFC antenna coil.
As the carrier frequency the NFC uses is 13.56 MHz and the read-write distance is short, the coupling mode of the NFC tag chip and the NFC card reader is magnetic field coupling, and coils can be used as the NFC antennas.
One advantage of the ordinary NFC tag is that it does not need power source, and the power source can be formed by receiving the electromagnetic energy emitted by the NFC card reader. However, the problem is that, as long as the NFC card reader is close to the NFC tag, the NFC tag will be activated, and the stored information will be automatically transmitted to the NFC card reader, which is not expected in some occasions. For example, in a Bluetooth headset equipped with the ordinary NFC tag, the Bluetooth headset pairing information such as Bluetooth address is stored in the NFC tag. When electronic equipment (such as NFC mobile phone) equipped with the NFC card reader is closed to the Bluetooth headset equipped with the NFC tag, the electronic equipment will read the headset pairing information such as Bluetooth address stored in the NFC tag of the Bluetooth headset through the NFC card reader so as to pair with the Bluetooth headset. In this situation, if the electronic equipment close to the Bluetooth headset, it can still read the pairing information stored in the Bluetooth headset even if the Bluetooth headset is turned off, thus initiating the Bluetooth protocol to pair with the Bluetooth headset actively.
As mentioned above, although the pairing will not be successful finally as the Bluetooth headset is turned off, the NFC card reader reading the information stored in the NFC tag unconditionally will cause some unnecessary operations and will affect the information security.